1. Field of the Invention
The present invention generally relates to a jaw folding device of a jaw-type folder which is suitable for roll paper. Particulary, the present invention relates to a jaw folding mechanism of a jaw cylinder of this jaw folding device for jaw folding papers to be printed to form a folded print. More particularly, the present invention relates to a jaw folding device for a jaw cylinder of a jaw-type folder which can be switched between a correct run mode for performing a duplicate folding and a straight run mode for performing an ordinary folding.
2. Description of the Prior Art
Conventional jaw folding devices for a jaw cylinder of a jaw folding device have been shown in "Offset Print" (first print issue, pp. 196 to pp. 200) published by Nippon Insatsu Shinbun-Sha (Japan Print Newspaper Company) on June 25, 1984; "Introduction of Printing Machine" (first edition print, pp. 64 to pp. 67) published by Insatsu Gakkai on Feb. 7, 1979; Japanese Patent Publication No. Sho. 47-51740; and Japanese Patent Publication No. Sho. 52-12612.
In such prior art, a jaw cylinder is provided with a pair of jaw folding devices in such a manner that they are symmetrically arranged on the circumferential surface of the cylinder about the axis of the cylinder. Under a straight run mode (ordinary folding mode), these jaw folding devices repeat opening and closing motions, so that each device performs jaw folding and feeding work of a paper section. On the other hand, under a correct run mode (duplicate folding mode), a previously printed paper (first section) is firstly wound around a folding cylinder and kept in such waiting state for a while, and secondly lapped with a subsequently printed paper (second section). Then these first and second sections are jaw-folded and fed to the succeeding step. Accordingly, under the correct run mode jaw folding action will be decreased in proportion to the number of waiting operations of the first section rather than the straight run mode. In detail, under the straight run mode two jaw folding devices on the cylinder alternatively perform jaw-folding action as the cylinder revolves. On the other hand, under the correct run mode only one of the jaw folding devices is actuated to perform the jaw folding action.
Therefore, in conventional manner the non-actuated one is removed from the cylinder or a jaw plate is removed from the non-actuated device during the correct run mode. This removing operation is conducted when the mode is switched from the straight run mode to the correct run mode.
However, this removing operation is complicated and thus causes the working efficiency and the operation rate of machine to become poor.